The function of tRNA synthetases is to attach amino acids to t...

Question

The function of tRNA synthetases is to attach amino acids to tRNAs. Suppose the tRNA synthetase responsible for attaching tryptophan to tRNA is mutated in a bacterial strain, with the result that the tRNA synthetase functions at about 15% of the efficiency of the wild-type tRNA synthetase.
How would this mutation affect attenuation of the tryptophan operon? Explain your answer.

How would this mutation affect attenuation of the tryptophan operon? Explain your answer.

Accepted Answer

Hi, everyone. Welcome back. Let's look at our next problem in a bacterial strain with a mutated T R N A synthetase that functions at approximately 15% of the efficiency of the wall type synthetase. What is the likely effect on the attenuation of the trip Toan operon in the presence of ample tripp Toan? We have four answer choices. A enhanced attenuation leading to increased transcription termination, be weakened attenuation leading to increased transcription, anti termination. C no change in attenuation with no effect on transcription or d complete abolition of attenuation allowing for continuous transcription. So let's briefly remind ourselves of the operation of this trip to Fan operon and how the attenuation process works. So we can think through the effect of the conditions mentioned in our problem. So obviously, the crypto Fan operon is governed by governed by the amount of Tripp toan present in low levels of trip to fame. We have a stalling in the process of transcription due to the fact that the leader peptide that preceeds the tripp toan genes requires two tripp toan residues. If there's low levels of krypto, the crypto fan is not available to fill those spots and it halts everything that leads to formation of the 23 stem loop, which is an anti termination structure. So transcription continues further down of the trip to fan jeans. So you have weakened attenuation if Ryan concentrations are high. So high Ryan, there is no stalling plenty of trip to to fill in those spots. The leader peptide is synthesized and that causes the formation down in the the further on of a 34 stem loop which causes the termination of transcription. So those are the general normal operating conditions. Well, we're talking about a bacterial strain that has a mutated T R N A synthetase. Well, our T R N A synthetase is what matches T R N A molecules with their amino acids. So sort of loads them up with an amino acid to bring on over in the synthesis of a peptide. So if our synthetase is mutated and is operating less efficiently, that will lead to increased stalling in the synthesis of the leader peptide. So if we just consider the situation of our mutation that would lead to weaken attenuation since our ribosome is more likely to stall at that point. However, the last part of our question tells us that we're in the presence of ample trip to and if there's plenty of crypto around, that's going to kind of override the effect of this mutation that T R N A synthesis. So the presence of loss of Tripp Toan being around will sort of mitigate that effect. And we'll click into that situation. Oops, excuse me, in choice a of an enhanced attenuation leading to increased transcription termination. So in this case, the conditions that we're in of ample crypto sort of override the effect of the mutated strain. So choice A here is going to be the answer we're looking for. We have enhanced attenuation leading to increased transcription termination. See you in the next video.

Key Concepts

tRNA Synthetases

Attenuation in Gene Regulation

Impact of Amino Acid Availability

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